Crystallographic and lithium-6 and nitrogen-15 NMR studies of a chiral bidentate lithium amide. An effect of aggregation states on an enantioselective deprotonation reaction

1992 ◽  
Vol 114 (2) ◽  
pp. 761-763 ◽  
Author(s):  
Daisaku Sato ◽  
Hisashi Kawasaki ◽  
Ichio Shimada ◽  
Yoji Arata ◽  
Kimio Okamura ◽  
...  
Keyword(s):  
Nmr Studies ◽  
Lithium Amide ◽  
Deprotonation Reaction ◽  
Enantioselective Deprotonation

Stereoselective reactions. 26. Solution structures of chiral bidentate lithium amide in relation to the solvent-dependent enantioselectivities in deprotonation reaction

Tetrahedron ◽  
1997 ◽  
Vol 53 (21) ◽  
pp. 7191-7200 ◽  
Author(s):  
Daisaku Sato ◽  
Hisashi Kawasaki ◽  
Ichio Shimada ◽  
Yoji Arata ◽  
Kimio Okamura ◽  
...  
Keyword(s):  
Lithium Amide ◽  
Solution Structures ◽  
Deprotonation Reaction ◽  
Stereoselective Reactions

1,3-Dioxan-5-ones: synthesis, deprotonation, and reactions of their lithium enolates

1995 ◽  
Vol 73 (10) ◽  
pp. 1616-1626 ◽  
Author(s):  
Marek Majewski ◽  
D. Mark Gleave ◽  
Pawel Nowak
Keyword(s):  
Enantiomeric Excess ◽  
Addition Reactions ◽  
Synthetic Route ◽  
Enol Ethers ◽  
Lithium Amide ◽  
Silyl Enol Ethers ◽  
Lithium Amides ◽  
Alkyl Groups ◽  
Lithium Enolates ◽  
Enantioselective Deprotonation

A general synthetic route to 2-alkyl- and 2,2-dialkyl-1,3-dioxan-5-ones, using tris(hydroxymethyl)-nitromethane as the starting material, is described. Deprotonation of these compounds was studied. It was established that these dioxanones could be deprotonated with LDA; however, the reduction of the carbonyl group via a hydride transfer from LDA, giving the corresponding dioxanols, often competed with deprotonation. The reduction could be minimized by using Corey's internal quench procedure to form silyl enol ethers and was less pronounced in 2,2-dialkyldioxanones (ketals) than in 2-alkyldioxanones (acetals). Self-aldol products were observed when dioxanone lithium enolates were quenched with H2O. Addition reactions of lithium enolates of dioxanones to aldehydes were threo-selective as predicted by the Zimmerman–Traxler model. Dioxanones having two different alkyl groups at the 2-position were deprotonated enantioselectively by chiral lithium amide bases with enantiomeric excess (ee) of up to 70%. Keywords: 1,3-dioxan-5-ones, enantioselective deprotonation, chiral lithium amides.

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